In the cast-in-place concrete construction method, reinforcing bars are assembled to a building framework in the field of construction, in which a reinforcing bar often has an end thereof connected to an end of the other reinforcing bar. In the precast concrete construction method, precast concrete members are assembled to a concrete building in the field of construction, in which, in most, one precast concrete member has at least one splice sleeve therein connected with an end of the respective reinforcing bar projected from the other member. Sometimes, it is needed that the both precast concrete members have the opposite ends of their respective reinforcing bars connected with each other and that the reinforcing bars are fixedly supported immediately after being abutted in the both construction methods. This needs such a mortar grout splice sleeve that is able to fixedly hold the reinforcing bar prior to mortar hardening.
The prior art sleeve has an inner diameter much larger than the outer diameter of the reinforcing bar because of being required to receive the reinforcing bar with a large tolerance. Therefore, the sleeve is unable to hold the reinforcing bar fixedly therein without mortar hardening. Conventionally, the following methods have been adopted for connecting the both ends of the opposite reinforcing bars and fixedly holding them at once after being connected. A pressure welding method connects thee both reinforcing bars by heating their abutted end faces with pressure. A butt welding method connects the both reinforcing bars by welding their abutted end portions. A lap joint method connects the both reinforcing bars by tying their overlapped end portions with steel wires. A screw-coupling method connects the both reinforcing bars by screwing their external threaded end portions into the internal threads of a coupling sleeve. However, both the pressure and butt welding methods require apparatus for heating the end portion of the reinforcing bar and worker's skillness. At any rate, it is difficult to realize a reliable welding work in the field of construction. Besides, the butt welding method requires a laborious preparation of the end face of the reinforcing bar prior to welding. The lap joint method requires the overlapped end portions of the bars to have an axial length by at least 20 times longer than the diameter of the bar. It is not suitable to diametrally large iron bars, because the overlapped portions of the diametrally large iron bars reduce an amount of concrete to an undesired one. The screw-coupling method disadvantageously requires an operation to thread the end portion of the reinforcing bar and rotate either of the reinforcing bar and the coupler. In addition, in case of the end-to-end connection of reinforcing bars of the precast concrete members, there is another problem that secondary stress produced by welding heat may give an undesirable influence to a positional relationship between the precast concrete members to be connected to each other. The present invention is intended to solve the problems as described above. It provides a mortar grout splice sleeve utilizable both in the cast-in-place and precast concrete construction methods. The sleeve receives the reinforcing bar fixedly prior to mortar hardening. The sleeve also makes an easy and reliable end-to-end connection between the both reinforcing bars without requiring any of a special device for heating, a laborious preparation, and skilled workers. The use of the inventive sleeve results in that the diametrally large reinforcing bars are connected to each other without reducing a desired amount of concrete, and that the precast members are free from an inconvenient secondary stress when connected to each other.